3. Vmax of the sodium-lithium countertransport was elevated in the hypertriglyceridaemic group compared with controls. Across the whole group loge triacylglycerols correlated with Vmax of the sodium-lithium countertransport. There was no difference in sodium-lithium countertransport Km between the groups.

4. Sodium-hydrogen maximal proton efflux rate (Vmax) and Km were not different between the three groups. There were no correlations between sodium—hydrogen exchange and sodium—lithium countertransport parameters.

5. Microviscosity as measured by diphenylhexatriene was reduced at the core of the membrane in subjects with hypertriglyceridaemia compared with those with familial hypercholesterolaemia or normolipaemic controls, suggesting an alteration in membrane structure.

6. Changes in sodium transport in hyperlipidaemia may be mediated by changes in membrane structure resulting in altered protein conformation or turnover.